
\begin{tabular}{rrrrrrr}
\toprule
\multicolumn{1}{c}{ } & \multicolumn{3}{c}{BRS} & \multicolumn{3}{c}{QCA} \\
\cmidrule(l{3pt}r{3pt}){2-4} \cmidrule(l{3pt}r{3pt}){5-7}
N & Num. Rules & Rule Len. & Accuracy & Num. Rules & Rule Len. & Accuracy\\
\midrule
25 & 2.11 & 2.46 & 0.56 & 2.81 & 2.57 & 0.55\\
100 & 1.30 & 2.91 & 0.62 & 7.42 & 4.09 & 0.57\\
250 & 1.21 & 2.98 & 0.65 & NA & NA & NA\\
500 & 1.55 & 2.94 & 0.68 & NA & NA & NA\\
750 & 1.76 & 2.95 & 0.68 & NA & NA & NA\\
\addlinespace
1000 & 2.15 & 2.96 & 0.70 & NA & NA & NA\\
\bottomrule
\end{tabular}
